Question

I have a model that needs to have an attribute added to it to tell whether it is live or not, for example a boolean called disabled that can be set to true. I have a large codebase already and I don’t want to add in an unless disabled == false condition to every query.

Is there some sort of before filter that I can run before every query to check this attribute?

Answer 1

You can use ActiveRecord default_scope statement. It will concatenate the scope you define to each query done through the model.

class MyModel < ActiveRecord::Base
  default_scope where(:disabled => false)
end

now running this:

MyModel.all

generates:

# => SELECT * FROM my_models WHERE disabled =false

The full documentation for it can be found here. I also made a post about the topic in my blog. There are some nice insights about default_scope I’d recommend going through before applying it.